Energy-dispersive X-ray spectroscopy (EDX) performed using scanning transmission electron microscopy (STEM) in combination with a windowless detector setup allows high-resolution imaging and chemical composition mapping even of light elements present in low concentrations. The used TEM-system combines a field emission electron source with four silicon drift detectors allowing for high detection sensitivity. We used this enhanced system to investigate 20 to 200 nm sized inclusions in milky diamonds from Rio Soriso, Juina area, Brazil. The diamonds act as a chemical inert container and therefore protect their inclusions from further chemical reactions with their surroundings. We visualize the presence and distribution of nitrogen within focused ion beam (FIB) slices containing these nanoinclusions. The investigation of these specific diamonds may open a new window to deeper parts of the Earth (>660 km) as they represent pristine material of this deep mantle environment.